Comparison of safety factors obtained from limit equilibrium methods and finite element analyses

Engin, Volkan
Toker, Nabi Kartal
Designing with limit equilibrium methods involves a factor of safety as a measure of stability, i.e. how far the resisting structure is from the limit state, on the safe side. On the other hand, current engineering practice employs finite element programs (such as PLAXIS) which, instead of using a conventionally-defined factor of safety, reduces the overall shear strength of the soil by introducing a reduction factor that is applied to soil strength (i.e. tan  and c values). Such fundamental differences in the incorporation of safety into the design process leads to different results from limit equilibrium methods and finite element simulations. In this parametric study, retaining walls, both cantilever and supported at a single level, with variable height and soil properties, are analyzed as example problems. For each case, multiple factors of safety are determined using different limit equilibrium methods found in the literature. In computer models, safety factor is defined in a variety of ways, based on; working and ultimate loads or stresses, normal & shear stresses along failure planes and reduction of soil strength.The safety factors from different methods are compared and relations between them were investigated by least squares regression analysis. Consequently, correlations among and between the safety factors obtained from limit equilibrium methods and finite element modeling results are proposed. Results of different limit equilibrium solution procedures are found to be linearly correlated with each other without involving soil strength parameters. Success of the FEM-based methods is found to vary based on the soil and support type.
3rd International Conference on New Developments in Soil Mechanics and Geotechnical Engineering


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Citation Formats
V. Engin and N. K. Toker, “Comparison of safety factors obtained from limit equilibrium methods and finite element analyses,” Lefkoşa, Cyprus (KKTC), 2012, p. 811, Accessed: 00, 2021. [Online]. Available: